Roof tiles are designed mainly to keep out weather elements especially rain. Tiles of various compositions have been used since ancient times to provide a protective membrane over building roof structures and are traditionally manufactured from clay. However, modern materials such as concrete and plastic are also used and some clay tiles incorporate a waterproof glaze. Other materials may include brick, stone, wood, metal (ferrous and non-ferrous), bituminous rubber or composite materials.
A typical roofing system comprises sheets of wood, typically plywood or decking material, nailed to the truss rafters to form a pitched roof deck. Typically, the pitched roof deck is overlaid with a roof substrate made of waterproofing material. Typically, the waterproofing material is a membrane made from modified bitumen impregnated fibreglass or polyester fibres. Roof components are primarily secured to the pitched roof deck with mechanical fasteners. Nails are the primary mechanical fasteners for securing roof components to a wood deck. Typically, tile roof components are secured with nails, inserted through holes in the tile roof component, driven into and through the roof substrate and wood deck. Mortar is sometimes used in conjunction with nails to provide holding force of the tile roof component to the roof deck.
It is well known that other typical roofing systems may include tiles which are directly attached to wooden cladding/battens of a roof.
It is also well known that a large proportion of heat can escape from the roof of a building and it has become apparent that over the last decade there has become a real need for a thermal aspect to roofing. In hot climates the ability to reduce the amount of heat entering a roof can result in greater energy efficiency through obviating the need to use air conditioning to a lesser extent.
The ‘R-Value’ is a measure of thermal resistance used in the building and construction industry. Under uniform conditions it is the ratio of the temperature difference across an insulator and the heat flux (heat transfer per unit area, through it). R-values are given in SI units, typically square-meter Kelvins per watt (m2K/W). Increasing the thickness of an insulating layer increases the thermal resistance. For example, doubling the thickness of fibreglass batting will double its R-value, perhaps from 2.0 m2 K/W for 110 mm thickness, up to 4.0 m2K/W for a 220 mm of thickness.
Tile manufacturers have been attempting to increase the insulation rating or ‘R-Value’ of tiles to prevent heat from escaping from the roof of a building. For example, U.S. Pat. No. 7,249,443 relates to an insulated pitched tile roofing system. In particular, the multi-layer component tile system comprises an insulating component which is a board or sheet material, preferably a Styrofoam sheet. The insulating component is preferably adhered to a roofing substrate, if used, or to decking material of a roof deck if the roof substrate is not used. Preferably, the sheet material comprises a substantially flat lower surface and an upper surface. The lower surface is preferably adhered to the roof substrate on the roof deck with a polymer adhesive. The roof tiles are preferably adhered to the upper surface of the sheet material with the polymer adhesive.
However, there are disadvantages associated with this multi-layer component system. The insulating component is not integrated into the tile and requires installation in addition to the roof tile. This is labour intensive requiring excessive installation time and hence increases the cost of installation. Furthermore, Styrofoam insulation material is highly flammable and when burning creates toxic smoke/fumes. Although Styrofoam material provides good insulating properties, it is well known that there are several health issues surrounding Styrofoam insulation such as being a suspected carcinogen. This is primarily due to the presence of certain organic chemicals used in the manufacturing of this material as well as the potential for continued exposure to trace amounts of these chemicals that remain in the finished product.
US 2010/0269440 relates to a roof tile having an integrated insulated foam core covered with a strengthening material (e.g., fibreglass mesh) and a thin outer cement-based protective coating (cured cement slurry). The cement-based protective coating comprises one or more additives to impart water repellent properties to the tile surface. The tile claims to be lightweight, strong, have a high fire-resistance rating, a high insulation rating and can be easily formed into various cross-sectional shapes to increase aesthetic appeal and offer ventilation to the underside of the tiles.
Although the roof tile disclosed in US 2010/0269440 comprises an integrated insulated foam core (which provides insulation and reduces installation costs), a disadvantage is the foam core is manufactured from harmful chemical agents. The present invention discloses that the foam core is expanded polystyrene (EPS). EPS is generally produced from a mixture of about 95% polystyrene and 5% gaseous blowing agent (e.g. pentane). Other types of foam disclosed include high density foam, Styrofoam, polystyrene, MDI monomer, polyurethane resins, extruded foam, expanded plastic foam, polyethylene and nylon.
The Insulite™ roof tile distributed by Insulite Hawaii is a further example of a roof tile that offers an integrated high density (EPS) foam core. Again, the foam is wrapped with a high strength alkaline resistant woven fibreglass mesh and each tile coated with a proprietary high strength cementitious coating. The distributor considers the tile to be lightweight, fire resistant while offering an average insulation value of R-6. However a disadvantage of this product is that the insulation barrier is again manufactured from harmful chemical agents.
Another method to increase the thermal properties of roof tiles is to apply a protective roof coating. For example, Industrial Nanotech, Inc manufacture a thin film insulation coating marketed as Nanusulate. Nansulate utilises a nanomaterial with a low thermal conductivity which allows the coating to inhibit heat transfer in a thin layer. It is recommended that three coats of Nansulate are applied with a brush, roller or paint sprayer for effective coverage. The product is configured for use with concrete or clay tile roofs, slate roof and asphalt or wood roofs.
However, there are disadvantages associated with this product. The application of three coats of the material to provide a thermal barrier is labour intensive (notwithstanding the additional cost associated with purchasing the material). Nansulate also contains non-environmentally friendly Volatile Organic Compounds (VOC).
From the above, it can be seen that it would be advantageous to have a roof tile with thermal insulation properties which is environmentally friendly, non-labour intensive to install and economical to manufacture.
It is an object of the present invention to address the foregoing disadvantages or at least to provide the public with a useful choice.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
Throughout this specification, the word “comprise”, or variations thereof such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.